Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 655 insertions, 0 deletions

diff --git a/net/sunrpc/auth_gss/gss_krb5_mech.c b/net/sunrpc/auth_gss/gss_krb5_mech.c
new file mode 100644
index 000000000..e31cfdf7e
--- /dev/null
+++ b/net/sunrpc/auth_gss/gss_krb5_mech.c
@@ -0,0 +1,655 @@
+// SPDX-License-Identifier: BSD-3-Clause
+/*
+ *  linux/net/sunrpc/gss_krb5_mech.c
+ *
+ *  Copyright (c) 2001-2008 The Regents of the University of Michigan.
+ *  All rights reserved.
+ *
+ *  Andy Adamson <andros@umich.edu>
+ *  J. Bruce Fields <bfields@umich.edu>
+ */
+
+#include <crypto/hash.h>
+#include <crypto/skcipher.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/sunrpc/auth.h>
+#include <linux/sunrpc/gss_krb5.h>
+#include <linux/sunrpc/xdr.h>
+#include <kunit/visibility.h>
+
+#include "auth_gss_internal.h"
+#include "gss_krb5_internal.h"
+
+#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
+# define RPCDBG_FACILITY	RPCDBG_AUTH
+#endif
+
+static struct gss_api_mech gss_kerberos_mech;
+
+static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = {
+#if defined(CONFIG_RPCSEC_GSS_KRB5_ENCTYPES_AES_SHA1)
+	/*
+	 * AES-128 with SHA-1 (RFC 3962)
+	 */
+	{
+	  .etype = ENCTYPE_AES128_CTS_HMAC_SHA1_96,
+	  .ctype = CKSUMTYPE_HMAC_SHA1_96_AES128,
+	  .name = "aes128-cts",
+	  .encrypt_name = "cts(cbc(aes))",
+	  .aux_cipher = "cbc(aes)",
+	  .cksum_name = "hmac(sha1)",
+	  .derive_key = krb5_derive_key_v2,
+	  .encrypt = gss_krb5_aes_encrypt,
+	  .decrypt = gss_krb5_aes_decrypt,
+
+	  .get_mic = gss_krb5_get_mic_v2,
+	  .verify_mic = gss_krb5_verify_mic_v2,
+	  .wrap = gss_krb5_wrap_v2,
+	  .unwrap = gss_krb5_unwrap_v2,
+
+	  .signalg = -1,
+	  .sealalg = -1,
+	  .keybytes = 16,
+	  .keylength = BITS2OCTETS(128),
+	  .Kc_length = BITS2OCTETS(128),
+	  .Ke_length = BITS2OCTETS(128),
+	  .Ki_length = BITS2OCTETS(128),
+	  .cksumlength = BITS2OCTETS(96),
+	  .keyed_cksum = 1,
+	},
+	/*
+	 * AES-256 with SHA-1 (RFC 3962)
+	 */
+	{
+	  .etype = ENCTYPE_AES256_CTS_HMAC_SHA1_96,
+	  .ctype = CKSUMTYPE_HMAC_SHA1_96_AES256,
+	  .name = "aes256-cts",
+	  .encrypt_name = "cts(cbc(aes))",
+	  .aux_cipher = "cbc(aes)",
+	  .cksum_name = "hmac(sha1)",
+	  .derive_key = krb5_derive_key_v2,
+	  .encrypt = gss_krb5_aes_encrypt,
+	  .decrypt = gss_krb5_aes_decrypt,
+
+	  .get_mic = gss_krb5_get_mic_v2,
+	  .verify_mic = gss_krb5_verify_mic_v2,
+	  .wrap = gss_krb5_wrap_v2,
+	  .unwrap = gss_krb5_unwrap_v2,
+
+	  .signalg = -1,
+	  .sealalg = -1,
+	  .keybytes = 32,
+	  .keylength = BITS2OCTETS(256),
+	  .Kc_length = BITS2OCTETS(256),
+	  .Ke_length = BITS2OCTETS(256),
+	  .Ki_length = BITS2OCTETS(256),
+	  .cksumlength = BITS2OCTETS(96),
+	  .keyed_cksum = 1,
+	},
+#endif
+
+#if defined(CONFIG_RPCSEC_GSS_KRB5_ENCTYPES_CAMELLIA)
+	/*
+	 * Camellia-128 with CMAC (RFC 6803)
+	 */
+	{
+		.etype		= ENCTYPE_CAMELLIA128_CTS_CMAC,
+		.ctype		= CKSUMTYPE_CMAC_CAMELLIA128,
+		.name		= "camellia128-cts-cmac",
+		.encrypt_name	= "cts(cbc(camellia))",
+		.aux_cipher	= "cbc(camellia)",
+		.cksum_name	= "cmac(camellia)",
+		.cksumlength	= BITS2OCTETS(128),
+		.keyed_cksum	= 1,
+		.keylength	= BITS2OCTETS(128),
+		.Kc_length	= BITS2OCTETS(128),
+		.Ke_length	= BITS2OCTETS(128),
+		.Ki_length	= BITS2OCTETS(128),
+
+		.derive_key	= krb5_kdf_feedback_cmac,
+		.encrypt	= gss_krb5_aes_encrypt,
+		.decrypt	= gss_krb5_aes_decrypt,
+
+		.get_mic	= gss_krb5_get_mic_v2,
+		.verify_mic	= gss_krb5_verify_mic_v2,
+		.wrap		= gss_krb5_wrap_v2,
+		.unwrap		= gss_krb5_unwrap_v2,
+	},
+	/*
+	 * Camellia-256 with CMAC (RFC 6803)
+	 */
+	{
+		.etype		= ENCTYPE_CAMELLIA256_CTS_CMAC,
+		.ctype		= CKSUMTYPE_CMAC_CAMELLIA256,
+		.name		= "camellia256-cts-cmac",
+		.encrypt_name	= "cts(cbc(camellia))",
+		.aux_cipher	= "cbc(camellia)",
+		.cksum_name	= "cmac(camellia)",
+		.cksumlength	= BITS2OCTETS(128),
+		.keyed_cksum	= 1,
+		.keylength	= BITS2OCTETS(256),
+		.Kc_length	= BITS2OCTETS(256),
+		.Ke_length	= BITS2OCTETS(256),
+		.Ki_length	= BITS2OCTETS(256),
+
+		.derive_key	= krb5_kdf_feedback_cmac,
+		.encrypt	= gss_krb5_aes_encrypt,
+		.decrypt	= gss_krb5_aes_decrypt,
+
+		.get_mic	= gss_krb5_get_mic_v2,
+		.verify_mic	= gss_krb5_verify_mic_v2,
+		.wrap		= gss_krb5_wrap_v2,
+		.unwrap		= gss_krb5_unwrap_v2,
+	},
+#endif
+
+#if defined(CONFIG_RPCSEC_GSS_KRB5_ENCTYPES_AES_SHA2)
+	/*
+	 * AES-128 with SHA-256 (RFC 8009)
+	 */
+	{
+		.etype		= ENCTYPE_AES128_CTS_HMAC_SHA256_128,
+		.ctype		= CKSUMTYPE_HMAC_SHA256_128_AES128,
+		.name		= "aes128-cts-hmac-sha256-128",
+		.encrypt_name	= "cts(cbc(aes))",
+		.aux_cipher	= "cbc(aes)",
+		.cksum_name	= "hmac(sha256)",
+		.cksumlength	= BITS2OCTETS(128),
+		.keyed_cksum	= 1,
+		.keylength	= BITS2OCTETS(128),
+		.Kc_length	= BITS2OCTETS(128),
+		.Ke_length	= BITS2OCTETS(128),
+		.Ki_length	= BITS2OCTETS(128),
+
+		.derive_key	= krb5_kdf_hmac_sha2,
+		.encrypt	= krb5_etm_encrypt,
+		.decrypt	= krb5_etm_decrypt,
+
+		.get_mic	= gss_krb5_get_mic_v2,
+		.verify_mic	= gss_krb5_verify_mic_v2,
+		.wrap		= gss_krb5_wrap_v2,
+		.unwrap		= gss_krb5_unwrap_v2,
+	},
+	/*
+	 * AES-256 with SHA-384 (RFC 8009)
+	 */
+	{
+		.etype		= ENCTYPE_AES256_CTS_HMAC_SHA384_192,
+		.ctype		= CKSUMTYPE_HMAC_SHA384_192_AES256,
+		.name		= "aes256-cts-hmac-sha384-192",
+		.encrypt_name	= "cts(cbc(aes))",
+		.aux_cipher	= "cbc(aes)",
+		.cksum_name	= "hmac(sha384)",
+		.cksumlength	= BITS2OCTETS(192),
+		.keyed_cksum	= 1,
+		.keylength	= BITS2OCTETS(256),
+		.Kc_length	= BITS2OCTETS(192),
+		.Ke_length	= BITS2OCTETS(256),
+		.Ki_length	= BITS2OCTETS(192),
+
+		.derive_key	= krb5_kdf_hmac_sha2,
+		.encrypt	= krb5_etm_encrypt,
+		.decrypt	= krb5_etm_decrypt,
+
+		.get_mic	= gss_krb5_get_mic_v2,
+		.verify_mic	= gss_krb5_verify_mic_v2,
+		.wrap		= gss_krb5_wrap_v2,
+		.unwrap		= gss_krb5_unwrap_v2,
+	},
+#endif
+};
+
+/*
+ * The list of advertised enctypes is specified in order of most
+ * preferred to least.
+ */
+static char gss_krb5_enctype_priority_list[64];
+
+static void gss_krb5_prepare_enctype_priority_list(void)
+{
+	static const u32 gss_krb5_enctypes[] = {
+#if defined(CONFIG_RPCSEC_GSS_KRB5_ENCTYPES_AES_SHA2)
+		ENCTYPE_AES256_CTS_HMAC_SHA384_192,
+		ENCTYPE_AES128_CTS_HMAC_SHA256_128,
+#endif
+#if defined(CONFIG_RPCSEC_GSS_KRB5_ENCTYPES_CAMELLIA)
+		ENCTYPE_CAMELLIA256_CTS_CMAC,
+		ENCTYPE_CAMELLIA128_CTS_CMAC,
+#endif
+#if defined(CONFIG_RPCSEC_GSS_KRB5_ENCTYPES_AES_SHA1)
+		ENCTYPE_AES256_CTS_HMAC_SHA1_96,
+		ENCTYPE_AES128_CTS_HMAC_SHA1_96,
+#endif
+	};
+	size_t total, i;
+	char buf[16];
+	char *sep;
+	int n;
+
+	sep = "";
+	gss_krb5_enctype_priority_list[0] = '\0';
+	for (total = 0, i = 0; i < ARRAY_SIZE(gss_krb5_enctypes); i++) {
+		n = sprintf(buf, "%s%u", sep, gss_krb5_enctypes[i]);
+		if (n < 0)
+			break;
+		if (total + n >= sizeof(gss_krb5_enctype_priority_list))
+			break;
+		strcat(gss_krb5_enctype_priority_list, buf);
+		sep = ",";
+		total += n;
+	}
+}
+
+/**
+ * gss_krb5_lookup_enctype - Retrieve profile information for a given enctype
+ * @etype: ENCTYPE value
+ *
+ * Returns a pointer to a gss_krb5_enctype structure, or NULL if no
+ * matching etype is found.
+ */
+VISIBLE_IF_KUNIT
+const struct gss_krb5_enctype *gss_krb5_lookup_enctype(u32 etype)
+{
+	size_t i;
+
+	for (i = 0; i < ARRAY_SIZE(supported_gss_krb5_enctypes); i++)
+		if (supported_gss_krb5_enctypes[i].etype == etype)
+			return &supported_gss_krb5_enctypes[i];
+	return NULL;
+}
+EXPORT_SYMBOL_IF_KUNIT(gss_krb5_lookup_enctype);
+
+static struct crypto_sync_skcipher *
+gss_krb5_alloc_cipher_v2(const char *cname, const struct xdr_netobj *key)
+{
+	struct crypto_sync_skcipher *tfm;
+
+	tfm = crypto_alloc_sync_skcipher(cname, 0, 0);
+	if (IS_ERR(tfm))
+		return NULL;
+	if (crypto_sync_skcipher_setkey(tfm, key->data, key->len)) {
+		crypto_free_sync_skcipher(tfm);
+		return NULL;
+	}
+	return tfm;
+}
+
+static struct crypto_ahash *
+gss_krb5_alloc_hash_v2(struct krb5_ctx *kctx, const struct xdr_netobj *key)
+{
+	struct crypto_ahash *tfm;
+
+	tfm = crypto_alloc_ahash(kctx->gk5e->cksum_name, 0, CRYPTO_ALG_ASYNC);
+	if (IS_ERR(tfm))
+		return NULL;
+	if (crypto_ahash_setkey(tfm, key->data, key->len)) {
+		crypto_free_ahash(tfm);
+		return NULL;
+	}
+	return tfm;
+}
+
+static int
+gss_krb5_import_ctx_v2(struct krb5_ctx *ctx, gfp_t gfp_mask)
+{
+	struct xdr_netobj keyin = {
+		.len	= ctx->gk5e->keylength,
+		.data	= ctx->Ksess,
+	};
+	struct xdr_netobj keyout;
+	int ret = -EINVAL;
+
+	keyout.data = kmalloc(GSS_KRB5_MAX_KEYLEN, gfp_mask);
+	if (!keyout.data)
+		return -ENOMEM;
+
+	/* initiator seal encryption */
+	keyout.len = ctx->gk5e->Ke_length;
+	if (krb5_derive_key(ctx, &keyin, &keyout, KG_USAGE_INITIATOR_SEAL,
+			    KEY_USAGE_SEED_ENCRYPTION, gfp_mask))
+		goto out;
+	ctx->initiator_enc = gss_krb5_alloc_cipher_v2(ctx->gk5e->encrypt_name,
+						      &keyout);
+	if (ctx->initiator_enc == NULL)
+		goto out;
+	if (ctx->gk5e->aux_cipher) {
+		ctx->initiator_enc_aux =
+			gss_krb5_alloc_cipher_v2(ctx->gk5e->aux_cipher,
+						 &keyout);
+		if (ctx->initiator_enc_aux == NULL)
+			goto out_free;
+	}
+
+	/* acceptor seal encryption */
+	if (krb5_derive_key(ctx, &keyin, &keyout, KG_USAGE_ACCEPTOR_SEAL,
+			    KEY_USAGE_SEED_ENCRYPTION, gfp_mask))
+		goto out_free;
+	ctx->acceptor_enc = gss_krb5_alloc_cipher_v2(ctx->gk5e->encrypt_name,
+						     &keyout);
+	if (ctx->acceptor_enc == NULL)
+		goto out_free;
+	if (ctx->gk5e->aux_cipher) {
+		ctx->acceptor_enc_aux =
+			gss_krb5_alloc_cipher_v2(ctx->gk5e->aux_cipher,
+						 &keyout);
+		if (ctx->acceptor_enc_aux == NULL)
+			goto out_free;
+	}
+
+	/* initiator sign checksum */
+	keyout.len = ctx->gk5e->Kc_length;
+	if (krb5_derive_key(ctx, &keyin, &keyout, KG_USAGE_INITIATOR_SIGN,
+			    KEY_USAGE_SEED_CHECKSUM, gfp_mask))
+		goto out_free;
+	ctx->initiator_sign = gss_krb5_alloc_hash_v2(ctx, &keyout);
+	if (ctx->initiator_sign == NULL)
+		goto out_free;
+
+	/* acceptor sign checksum */
+	if (krb5_derive_key(ctx, &keyin, &keyout, KG_USAGE_ACCEPTOR_SIGN,
+			    KEY_USAGE_SEED_CHECKSUM, gfp_mask))
+		goto out_free;
+	ctx->acceptor_sign = gss_krb5_alloc_hash_v2(ctx, &keyout);
+	if (ctx->acceptor_sign == NULL)
+		goto out_free;
+
+	/* initiator seal integrity */
+	keyout.len = ctx->gk5e->Ki_length;
+	if (krb5_derive_key(ctx, &keyin, &keyout, KG_USAGE_INITIATOR_SEAL,
+			    KEY_USAGE_SEED_INTEGRITY, gfp_mask))
+		goto out_free;
+	ctx->initiator_integ = gss_krb5_alloc_hash_v2(ctx, &keyout);
+	if (ctx->initiator_integ == NULL)
+		goto out_free;
+
+	/* acceptor seal integrity */
+	if (krb5_derive_key(ctx, &keyin, &keyout, KG_USAGE_ACCEPTOR_SEAL,
+			    KEY_USAGE_SEED_INTEGRITY, gfp_mask))
+		goto out_free;
+	ctx->acceptor_integ = gss_krb5_alloc_hash_v2(ctx, &keyout);
+	if (ctx->acceptor_integ == NULL)
+		goto out_free;
+
+	ret = 0;
+out:
+	kfree_sensitive(keyout.data);
+	return ret;
+
+out_free:
+	crypto_free_ahash(ctx->acceptor_integ);
+	crypto_free_ahash(ctx->initiator_integ);
+	crypto_free_ahash(ctx->acceptor_sign);
+	crypto_free_ahash(ctx->initiator_sign);
+	crypto_free_sync_skcipher(ctx->acceptor_enc_aux);
+	crypto_free_sync_skcipher(ctx->acceptor_enc);
+	crypto_free_sync_skcipher(ctx->initiator_enc_aux);
+	crypto_free_sync_skcipher(ctx->initiator_enc);
+	goto out;
+}
+
+static int
+gss_import_v2_context(const void *p, const void *end, struct krb5_ctx *ctx,
+		gfp_t gfp_mask)
+{
+	u64 seq_send64;
+	int keylen;
+	u32 time32;
+
+	p = simple_get_bytes(p, end, &ctx->flags, sizeof(ctx->flags));
+	if (IS_ERR(p))
+		goto out_err;
+	ctx->initiate = ctx->flags & KRB5_CTX_FLAG_INITIATOR;
+
+	p = simple_get_bytes(p, end, &time32, sizeof(time32));
+	if (IS_ERR(p))
+		goto out_err;
+	/* unsigned 32-bit time overflows in year 2106 */
+	ctx->endtime = (time64_t)time32;
+	p = simple_get_bytes(p, end, &seq_send64, sizeof(seq_send64));
+	if (IS_ERR(p))
+		goto out_err;
+	atomic64_set(&ctx->seq_send64, seq_send64);
+	/* set seq_send for use by "older" enctypes */
+	atomic_set(&ctx->seq_send, seq_send64);
+	if (seq_send64 != atomic_read(&ctx->seq_send)) {
+		dprintk("%s: seq_send64 %llx, seq_send %x overflow?\n", __func__,
+			seq_send64, atomic_read(&ctx->seq_send));
+		p = ERR_PTR(-EINVAL);
+		goto out_err;
+	}
+	p = simple_get_bytes(p, end, &ctx->enctype, sizeof(ctx->enctype));
+	if (IS_ERR(p))
+		goto out_err;
+	ctx->gk5e = gss_krb5_lookup_enctype(ctx->enctype);
+	if (ctx->gk5e == NULL) {
+		dprintk("gss_kerberos_mech: unsupported krb5 enctype %u\n",
+			ctx->enctype);
+		p = ERR_PTR(-EINVAL);
+		goto out_err;
+	}
+	keylen = ctx->gk5e->keylength;
+
+	p = simple_get_bytes(p, end, ctx->Ksess, keylen);
+	if (IS_ERR(p))
+		goto out_err;
+
+	if (p != end) {
+		p = ERR_PTR(-EINVAL);
+		goto out_err;
+	}
+
+	ctx->mech_used.data = kmemdup(gss_kerberos_mech.gm_oid.data,
+				      gss_kerberos_mech.gm_oid.len, gfp_mask);
+	if (unlikely(ctx->mech_used.data == NULL)) {
+		p = ERR_PTR(-ENOMEM);
+		goto out_err;
+	}
+	ctx->mech_used.len = gss_kerberos_mech.gm_oid.len;
+
+	return gss_krb5_import_ctx_v2(ctx, gfp_mask);
+
+out_err:
+	return PTR_ERR(p);
+}
+
+static int
+gss_krb5_import_sec_context(const void *p, size_t len, struct gss_ctx *ctx_id,
+			    time64_t *endtime, gfp_t gfp_mask)
+{
+	const void *end = (const void *)((const char *)p + len);
+	struct  krb5_ctx *ctx;
+	int ret;
+
+	ctx = kzalloc(sizeof(*ctx), gfp_mask);
+	if (ctx == NULL)
+		return -ENOMEM;
+
+	ret = gss_import_v2_context(p, end, ctx, gfp_mask);
+	memzero_explicit(&ctx->Ksess, sizeof(ctx->Ksess));
+	if (ret) {
+		kfree(ctx);
+		return ret;
+	}
+
+	ctx_id->internal_ctx_id = ctx;
+	if (endtime)
+		*endtime = ctx->endtime;
+	return 0;
+}
+
+static void
+gss_krb5_delete_sec_context(void *internal_ctx)
+{
+	struct krb5_ctx *kctx = internal_ctx;
+
+	crypto_free_sync_skcipher(kctx->seq);
+	crypto_free_sync_skcipher(kctx->enc);
+	crypto_free_sync_skcipher(kctx->acceptor_enc);
+	crypto_free_sync_skcipher(kctx->initiator_enc);
+	crypto_free_sync_skcipher(kctx->acceptor_enc_aux);
+	crypto_free_sync_skcipher(kctx->initiator_enc_aux);
+	crypto_free_ahash(kctx->acceptor_sign);
+	crypto_free_ahash(kctx->initiator_sign);
+	crypto_free_ahash(kctx->acceptor_integ);
+	crypto_free_ahash(kctx->initiator_integ);
+	kfree(kctx->mech_used.data);
+	kfree(kctx);
+}
+
+/**
+ * gss_krb5_get_mic - get_mic for the Kerberos GSS mechanism
+ * @gctx: GSS context
+ * @text: plaintext to checksum
+ * @token: buffer into which to write the computed checksum
+ *
+ * Return values:
+ *    %GSS_S_COMPLETE - success, and @token is filled in
+ *    %GSS_S_FAILURE - checksum could not be generated
+ *    %GSS_S_CONTEXT_EXPIRED - Kerberos context is no longer valid
+ */
+static u32 gss_krb5_get_mic(struct gss_ctx *gctx, struct xdr_buf *text,
+			    struct xdr_netobj *token)
+{
+	struct krb5_ctx *kctx = gctx->internal_ctx_id;
+
+	return kctx->gk5e->get_mic(kctx, text, token);
+}
+
+/**
+ * gss_krb5_verify_mic - verify_mic for the Kerberos GSS mechanism
+ * @gctx: GSS context
+ * @message_buffer: plaintext to check
+ * @read_token: received checksum to check
+ *
+ * Return values:
+ *    %GSS_S_COMPLETE - computed and received checksums match
+ *    %GSS_S_DEFECTIVE_TOKEN - received checksum is not valid
+ *    %GSS_S_BAD_SIG - computed and received checksums do not match
+ *    %GSS_S_FAILURE - received checksum could not be checked
+ *    %GSS_S_CONTEXT_EXPIRED - Kerberos context is no longer valid
+ */
+static u32 gss_krb5_verify_mic(struct gss_ctx *gctx,
+			       struct xdr_buf *message_buffer,
+			       struct xdr_netobj *read_token)
+{
+	struct krb5_ctx *kctx = gctx->internal_ctx_id;
+
+	return kctx->gk5e->verify_mic(kctx, message_buffer, read_token);
+}
+
+/**
+ * gss_krb5_wrap - gss_wrap for the Kerberos GSS mechanism
+ * @gctx: initialized GSS context
+ * @offset: byte offset in @buf to start writing the cipher text
+ * @buf: OUT: send buffer
+ * @pages: plaintext to wrap
+ *
+ * Return values:
+ *    %GSS_S_COMPLETE - success, @buf has been updated
+ *    %GSS_S_FAILURE - @buf could not be wrapped
+ *    %GSS_S_CONTEXT_EXPIRED - Kerberos context is no longer valid
+ */
+static u32 gss_krb5_wrap(struct gss_ctx *gctx, int offset,
+			 struct xdr_buf *buf, struct page **pages)
+{
+	struct krb5_ctx	*kctx = gctx->internal_ctx_id;
+
+	return kctx->gk5e->wrap(kctx, offset, buf, pages);
+}
+
+/**
+ * gss_krb5_unwrap - gss_unwrap for the Kerberos GSS mechanism
+ * @gctx: initialized GSS context
+ * @offset: starting byte offset into @buf
+ * @len: size of ciphertext to unwrap
+ * @buf: ciphertext to unwrap
+ *
+ * Return values:
+ *    %GSS_S_COMPLETE - success, @buf has been updated
+ *    %GSS_S_DEFECTIVE_TOKEN - received blob is not valid
+ *    %GSS_S_BAD_SIG - computed and received checksums do not match
+ *    %GSS_S_FAILURE - @buf could not be unwrapped
+ *    %GSS_S_CONTEXT_EXPIRED - Kerberos context is no longer valid
+ */
+static u32 gss_krb5_unwrap(struct gss_ctx *gctx, int offset,
+			   int len, struct xdr_buf *buf)
+{
+	struct krb5_ctx	*kctx = gctx->internal_ctx_id;
+
+	return kctx->gk5e->unwrap(kctx, offset, len, buf,
+				  &gctx->slack, &gctx->align);
+}
+
+static const struct gss_api_ops gss_kerberos_ops = {
+	.gss_import_sec_context	= gss_krb5_import_sec_context,
+	.gss_get_mic		= gss_krb5_get_mic,
+	.gss_verify_mic		= gss_krb5_verify_mic,
+	.gss_wrap		= gss_krb5_wrap,
+	.gss_unwrap		= gss_krb5_unwrap,
+	.gss_delete_sec_context	= gss_krb5_delete_sec_context,
+};
+
+static struct pf_desc gss_kerberos_pfs[] = {
+	[0] = {
+		.pseudoflavor = RPC_AUTH_GSS_KRB5,
+		.qop = GSS_C_QOP_DEFAULT,
+		.service = RPC_GSS_SVC_NONE,
+		.name = "krb5",
+	},
+	[1] = {
+		.pseudoflavor = RPC_AUTH_GSS_KRB5I,
+		.qop = GSS_C_QOP_DEFAULT,
+		.service = RPC_GSS_SVC_INTEGRITY,
+		.name = "krb5i",
+		.datatouch = true,
+	},
+	[2] = {
+		.pseudoflavor = RPC_AUTH_GSS_KRB5P,
+		.qop = GSS_C_QOP_DEFAULT,
+		.service = RPC_GSS_SVC_PRIVACY,
+		.name = "krb5p",
+		.datatouch = true,
+	},
+};
+
+MODULE_ALIAS("rpc-auth-gss-krb5");
+MODULE_ALIAS("rpc-auth-gss-krb5i");
+MODULE_ALIAS("rpc-auth-gss-krb5p");
+MODULE_ALIAS("rpc-auth-gss-390003");
+MODULE_ALIAS("rpc-auth-gss-390004");
+MODULE_ALIAS("rpc-auth-gss-390005");
+MODULE_ALIAS("rpc-auth-gss-1.2.840.113554.1.2.2");
+
+static struct gss_api_mech gss_kerberos_mech = {
+	.gm_name	= "krb5",
+	.gm_owner	= THIS_MODULE,
+	.gm_oid		= { 9, "\x2a\x86\x48\x86\xf7\x12\x01\x02\x02" },
+	.gm_ops		= &gss_kerberos_ops,
+	.gm_pf_num	= ARRAY_SIZE(gss_kerberos_pfs),
+	.gm_pfs		= gss_kerberos_pfs,
+	.gm_upcall_enctypes = gss_krb5_enctype_priority_list,
+};
+
+static int __init init_kerberos_module(void)
+{
+	int status;
+
+	gss_krb5_prepare_enctype_priority_list();
+	status = gss_mech_register(&gss_kerberos_mech);
+	if (status)
+		printk("Failed to register kerberos gss mechanism!\n");
+	return status;
+}
+
+static void __exit cleanup_kerberos_module(void)
+{
+	gss_mech_unregister(&gss_kerberos_mech);
+}
+
+MODULE_LICENSE("GPL");
+module_init(init_kerberos_module);
+module_exit(cleanup_kerberos_module);